In January 2005, David Bell proposed to build a caterpillar like structure based on glider reflecting and glider duplicating *WSS convoys. I thought with the new slow salvo machinery, this idea is now in reach of actual construction.

The spine would be built of a downstream series of a *WSS convoy, the left side reflecting a glider while the right side duplicates it repeatedly. This uses standard reactions as they are contained e.g. in Jason Summer's colllection.

The duplicated gliders form the rakes used to build an upstream HWSS-helix. This helix in turn is needed to created the new *WSS for the downstream spine.

I'll post an example spine as soon as I get to it. This is of course more a vague idea than a concrete implementation.

E.g. one would need an efficient mechanism to destroy the downstream convoys. The only idea I came up with would be a downstram helix running with negative speed that sends out gliders stopping the *WSS.

HartmutHolzwart wrote:E.g. one would need an efficient mechanism to destroy the downstream convoys. The only idea I came up with would be a downstram helix running with negative speed that sends out gliders stopping the *WSS.

In the worst case you can build an additional negative speed downward helix, that emits a glider that destroys the main spine. But I think it would be feasible to combine it with either part of the spine. A bigger problem would be definitely to build the front. Just imagine, that merely burning the upward helix would have to result in a non-trivial downward spaceship stream!

That is what I imagine! One cycle convoy would be about 6 to 8 downward *WSS.

And this convoy would have to be built fast enough so that the next cycle is ready in time.

I imagine two more or less symmetric spines supporting a lef and a right burning helix, so that the downward gliders ejected by the burning helices from the left and right sides could be combined to build the downward *WSS. Pretty similar to the current caterpillar frontend, only that it builds *WSS instead of blinkers with pairs of synchronized gliders.

Just for a rough estimation: Imagine a speed of around c/6 and a period of around 200 gens.

It might be possible to make Caterpillar spaceships out of just standardspaceships with no exotic crawling reaction required. The idea is verysimple, so please let me know whether it could really work! If it doeswork, it should be possible to create Caterpillars with lots of differentspeeds.

To illustrate the idea:

Using an appropriate helix, create two downward moving streams ofstandard spaceship convoys one of which can perform a glider duplicationreaction and the other a glider reflection reaction. (These convoys takethe place of the blinkers in the existing Caterpillar. They are muchmore complicated to build from a helix than just blinkers, but it shouldstill be possible.)

For the "exotic" crawling reaction, just use a glider! It just bouncesback and forth between the glider duplication and reflection convoys,slowly moving upwards, liberating an output glider at each encounter witha glider duplication reaction.

Multiple gliders can be running through the glider duplication convoys atthe same time to create lots of output gliders, just like multiple PIsrun through the existing Caterpillar.

These output gliders are then used to construct the helix which thencompletes the loop.

I don't think that there is a need to multiply the base period of thereaction like the 6x in the existing Caterpillar. The helix only has togenerate a single set of convoys since the spacing of the glider reactionscan be adjusted to match. Similarly, there is no need for a filter streamfor the output gliders.

The speed of the Caterpillar is determined by the upwards speed of thegliders between the times that they are duplicated and turned, so itwould be near c/4, but slightly different due to the reactions involved.Since the spacing of the two convoys is adjustable, the actual speed canalso be adjusted. The further apart the convoys are, the closer the speedwould be to c/4. I can think of ways to adjust the speed further, suchas having one of the glider paths go backwards to make a VERY slowspaceship (but I don't know if this can work), or using a "catch and throw"reaction to delay when the glider is sent back on its way.

Finally, in practice, more convoys would actually be needed. For example,for the left and right side, for forwards and backward glider duplications,for phase and color capabilities, and for "catch and throw" reactions.This are details which I haven't thought about and which someone elsecan investigate.

[I just realized that even glider bouncing isn't really necessary. A stilllife can be activated by a passing convoy to create an output glider,and then recreated a bit forwards in the spaceship so that the next convoycan reuse it (to create a VERY slow spaceship again.) So this is somethingelse which can be investigated.]

David Bell wrote:I just realized that even glider bouncing isn't really necessary. A stilllife can be activated by a passing convoy to create an output glider,and then recreated a bit forwards in the spaceship so that the next convoycan reuse it (to create a VERY slow spaceship again.) So this is somethingelse which can be investigated.

This is an interesting side note. It seems very promising, especially because it might reduce amount of downward spaceships.

Something like the following would probably work, only if the loaf were re-created on the same vertical line and somewhat farther in order to have some space for slow salvo synthesis.

HartmutHolzwart wrote:E.g. one would need an efficient mechanism to destroy the downstream convoys. The only idea I came up with would be a downstram helix running with negative speed that sends out gliders stopping the *WSS.

Negative speed helices are comparatively simple, if we can use the loaf tractor beam reaction. I imagine that there would be two sections to the ship: the front section builds the forward helices to create the spine *WSSs, and a smaller back section that builds the downward helices to delete them.

The back two LWSSs and the overall period can be tuned as needed to match the speed of the ship overall. The issue here is that the loaf moves 6 cells every period, which may be incompatible with the spacing of the most compact spine.

Once thing I notice is that we don't need rephasers for the engineless caterpillar, which could save a lot of room. If a still life or bouncing glider is in the wrong position, we can move it up or down by two cells (assuming a vertical orientation of the ship) and it will work fine. However, moving only one cell will not work, since *WSSs are p4 instead of p2 in their c/2 movement. This means that every glider liberated by the still life/bouncing glider is going to be the same color. So unless we use two spine of two different colors, this is a monochromatic slow salvo problem. The question is whether it's more efficient to A) use monochromatic slow-salvo tech and build only one spine or B) have freedom of color but need to build twice as much. From the work on the half-baked knightship, I'm leaning towards A), but I'm not the expert here.

Some far-from-exhaustive tinkering gives this: Five spaceships can displace a block by 5 spaces and liberate a glider. With this convoy, the maximum speed for the overall ship is 5c/215, or c/43. It involves two LWSSs, two MWSSs, and one HWSS.

Since the *WSS slow-salvo synthesis is going to be expensive--look at how huge the Caterpillar is when it's only making blinkers--lots of searching should go into making the convoys as small (as in, few *WSSs) as possible before we do anything else. Getting this down to 4 *WSSs is probably doable by a search script or something, and maybe down to 3 if a target other than a block is used. Two *WSSs are needed to make a block explode into something usable, but a loaf can be activated with only one, for example.

...Also, the above doesn't play nice with the tractor-loaf helix, which moves up by 6 cells every period as opposed to the above's 5 cells. Ideally, the block should be displaced by a multiple of 6, so we only need one set of negative helixes to delete the convoys.

Of course you would need some filter mechanism like in the caterpliiar construction, as the helix would not be x1. Estimating from the other examples, a height of abbout thirty should suffice, so it would be say x6.

The caterpillar front end uses abount 60 additional *WSS to the left and to the right to generate 24 gliders that produce 12 gliders for two tracks due to the x6 multiplying (not counting the burning helix stuff!).

As you can basically use a two or even threesided glider construction, 10 *WSS would amount to 40 coordinated gliders, for that you would then need about 240 upstream *WSS for glider duplication and putting them on the right lane and timing.

While this looks like a quite challenging engeneering task, it looks to me that you are absolutely capable of doing that given enough time and dedication.

If we plan to address more of these projects, some dedicated tools for front end generation are a must, I would think.

HartmutHolzwart wrote:Of course you would need some filter mechanism like in the caterpliiar construction, as the helix would not be x1.

Not really. If you use still-lifes instead of gliders for encoding recipes you can extend the period as much as you want. In this case it would probably be worth to spend a couple more of spaceships to lengthen the step, than building about 6 times more spaceships with fanout devices.

Might be useful if I find other block transformations that don't emit gliders.

EDIT: 4 MWSSes can shift a block by 5. So, by chaining these onto the 5-and-glider before, we can get a block displacement of 30. This is just to establish a baseline; I'm not settling for 25 (!) *WSSs being necessary.

NOTE: 4 *WSS is probably reachable, but it's not a "huge" improvement, and will probably not move the blocks so far away, so the slow salvo might be a bit tight. I think in current circumstances this is more than enough to move on to the slow salvo and helix recipes.

NOTE2 We probably need odd step so 38 is a bit of a problem. But this recipe idea should work in various ways.

EDIT Unfortunately all the possible combinations of R/G converters yield similar results, for example:

Now left to find forward glider with good recovery, and maybe to give a try to 4 *WSS helix for the backward. Then we can pass to other parts (head using the helix, tail (probably using negative helix) and slow salvo recipes).

Run some pretty extensive search for 5 and forward glider and 4 for any glider with 0 results so far, so I guess we'll have to live with what we have. 5 for backward and 6 for forward, while the recipes are differ in only single *WSS (which is great feature for design). It's also not that bad, and I can't believe in possibility of drastic improvement (like 3 for backward or 4 for forward, because step of 38 is too large). So the recipes are very much OK, being close enough to the best as far as I'm concerned.

Last edited by simsim314 on November 11th, 2014, 2:27 am, edited 3 times in total.

The velocity I'm aiming for is 38 /(416 + N). 38 is the step of the 5 *WSS recipe. 416 is the minimal recovery time. It might be for some reason I don't see yet 38 /(416 + 2 * N) or something of this sort.

I'm sure you get Bell's idea, but here is a small demonstration using the relevant recipe:

This is pretty interesting, making the minimal speed a bit below c/9. I guess if this design will work out, it will allow design for all lower speeds as a consequence (using small modification on the caterpillar).

EDIT2 Just a side note concerning the speed limitation of this approach. Ignoring for a moment the helix speed issues, the signal can be made to travel as close to glider travel speed as we want to. Making it possible to reach any speed lower (but not equal) to c/4, with not too high cost.

EDIT3 Another point to notice is that it's in principle possible to find such signal that will travel even faster than c/2. Making the helix the only limitation of such approach. And as I remember (reading somewhere, and I can't find it now) helixes have some very specific limitation somewhere below c/2 because they use interactions between glider and *WSS which is somehow limited, but in my opinion it's also possible to built helix as fast as we want to (up to c/2), in the same way - the limitation only concerns gliders but there are many other ways and signals that can be part of helix, and they could travel pretty fast.